Completes job9/5a3de92 (which only cleaned commit-changer). These 3 execution
agents still emitted the banned trailer into their commit-message templates;
the settings.attribution backstop does not filter agent-authored message bodies.
Extended sweep of agents/ lib/ hooks/ templates/ for Co-Authored-By|Claude-Session|
--trailer now returns zero. Review finding A1 (BLOQUANT), J4-16 follow-up.